1. Field of the Invention
The present invention relates to an electromagnetic switch device for a starter, which includes a pinion-pushing solenoid for pushing out a pinion of the starter toward a ring gear and a motor-energizing solenoid for switching on and off a current supplied to a motor.
2. Description of Related Art
There is known a tandem solenoid-type electromagnetic switch device for a starter, which includes two solenoids. One of the two solenoids is a pinion-pushing solenoid for pushing out a pinion of the starter toward a ring gear of an engine, and the other is a motor-energizing solenoid for opening and closing a main contact provided in a current supply circuit of the motor. The tandem solenoid-type electromagnetic switch device is capable of controlling timing to push out the pinion and timing to start the motor independently.
In one known method, the motor-energizing solenoid is driven a predetermined time ΔTx after the pinion-pushing solenoid starts to be driven in response to a command to drive the motor after the pinion abuts against the ring gear. The time ΔTx is ideally a design value of the time elapsed from when the pinion-pushing solenoid starts to be driven to when the pinion abuts against the ring gear. This time is referred to as the “abutment time” hereinafter. However, the abutment time may deviate from the design value depending on the state of a battery, the ambient temperature, variation of the distance between the pinion and the ring gear due to the mounting tolerance on the engine. Accordingly, since the time ΔTx has to be set longer than the design value, the responsiveness is degraded.
In addition, when the time to start during the motor-energizing solenoid is set to the time ΔTx, if the actual abutment time becomes longer than the time ΔTx, there is a possibility that there occurs an engagement failure because the motor starts rotate before the pinion abuts against the ring gear.
Accordingly, it is desired to precisely detect the actual timing at which the pinion and the ring gear abut against each other. Japanese Patent Application Laid-open No. 2012-41859 describes a technique of predicting the timing at which a pinion and a ring gear abut against each other based on inverse rotation engagement. However, this technique cannot be used if the inverse rotation amount of the engine is not sufficiently large.
Japanese Patent Application Laid-open No. 2013-2381 describes a technique applicable to an electromagnetic switch device having the structure in which, between a first coil of a pinion-pushing solenoid and a second coil of a motor-energizing solenoid, a core which is shared by their magnetic circuits is disposed, the technique being for measuring a voltage induced in the coil of the motor-energizing solenoid when the pinion-pushing solenoid abuts against this core. However, this technique cannot be used other than for the structure in which the pinion-pushing solenoid and the motor-energizing solenoid share a core disposed between the first and second coils as part of their magnetic circuits.